tuning - pilot jet question

[G22inSC]

I decided to finally try and check to see if I had the correct pilot installed. The bike is 05 KDX200 with aftermarket pipe and exhaust with the airbox lid removed. I pulled the carb to make sure of the pilot (42) and then warmed the motor. I followed the typical jetting instructions...

"Turn the airscrew slowly in, and then out, until you find the point where the idle is fastest. Stop there. Now is the time to determine if you have the correct pilot installed in your carb. The airscrew position determines this for you, making it very simple. If your airscrew is less than 1 turn from closed, you need a larger pilot jet. If it is more than 2.5 turns from closed, you need a smaller pilot jet."

The way I understand this is to turn the airscrew in and out until you find the fastest idle (highest RPM). That is where my problems begin. The idle continues to increase the farther out I turn the airscrew. There is no up and down to the RPM's, it is just all up as you turn the airscrew out from fully seated. Am I doing this wrong or does that just mean my pilot is to large to see a midpoint where the RPM's fluctuate and that I need a smaller pilot? I am just not sure if I want to go much smaller on the pilot.

 

[_JOE_]

How long did you ride the bike before you did this?


If you can't get it to level out, try putting it back to where you started and tune it as you ride. Keep going out until the throttle response stops getting better.

 

[G22inSC]

I've had the bike for a few years now. It came stock with a 48 pilot which was way to rich. I have used a 45 and now a 42; however, I think the 42 may still be a little rich. I just don't want to go to low to quick.

 

[whenfoxforks-ruled]

You are on the right track. Run the engine just off idle and do a plug chop. Wet or dry? Chances are its too fat, and that is why your air screw is ineffective. I do not think running the pilot lean is as dangerous as running the main lean. Trail riding, I would like good steady response off bottom. No surge of power 2 milliseconds after you turn the throttle. Instant response. When it gets lean it will be real erratic.

 

[Rich Rohrich]

You are on the right track. Run the engine just off idle and do a plug chop. Wet or dry?

You can't read the pilot jetting by doing a plug chop ya goof. :rotfl:

Lean the pilot till it starts to feel flat, then go just a bit richer than that. Pilot jetting is all about what feels good to you, and gives you the response you want.

You can't hurt the engine by going to lean on the pilot.

 

[_JOE_]

You can't hurt the engine by going to lean on the pilot.

But you sure can make it hard start, lol!

 

[whenfoxforks-ruled]

If you are running it at say 1/4th throttle, for a few seconds, chop it, pull it, and if its wet assume that the pilot is big? I mean, your not"reading the plug", just is it wet or dry? Ride test always, lean effects the throttle response awful!

 

[Rich Rohrich]

If you are running it at say 1/4th throttle, for a few seconds, chop it, pull it, and if its wet assume that the pilot is big?

Regardless of what it looks like, you won't know if it's the result of the pilot or the needle, and you won't be able to maintain the same load on the engine from run to run. Setting it by feel is the only practical way for the average guy to get the pilot jetting set.

 

[whenfoxforks-ruled]

Well one thing is for sure. If you get too lean, a 30 second ride will tell you how crappy it is running, and should not kill the bike. Nice and smooth, every time off idle. Sometimes it matters. JD jetting covers kdx's.

 

[Rich Rohrich]

Well one thing is for sure. If you get too lean, a 30 second ride will tell you how crappy it is running, and should not kill the bike.

On that we agree 100%. :cool: